package offer;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;

/**
 * <p>
 * 剑指 Offer 32 - II. 从上到下打印二叉树 II
 * </p>
 *
 * @author xiaozuolin
 * @date 2021/9/24 8:54
 */
public class Offer32_2 {
    public List<List<Integer>> levelOrder(TreeNode root) {
        Queue<TreeNode> queue = new LinkedList<>();
        List<List<Integer>> res = new ArrayList<>();
        if (root != null) {
            queue.add(root);
        }
        while (!queue.isEmpty()) {
            List<Integer> tmp = new ArrayList<>();
            for (int i = queue.size(); i > 0; i--) {
                TreeNode node = queue.poll();
                tmp.add(node.val);
                if (node.left != null) {
                    queue.add(node.left);
                }
                if (node.right != null) {
                    queue.add(node.right);
                }
            }
            res.add(tmp);
        }
        return res;
    }
}
